Regulating system



Sept. 22, 1936. P, M STWENDER 2,055,138

REGULATING SYSTEM Filed Dec. 8, 1953 2 Sheets-Sheet l mom/wg SePt- 22, 1936- P. M. s-nvENDR 2,055,138

REGULATING SYSTEM Filed Dec. 8, 1953 2 Sheets-Sheet 2 Patented Sept. 22, v1936 'UNITED STATES REGULATING SYSTEM Paul M. `Stivender, West Allis, Wis., asngnor to Allis-Chalmers Manufacturing'company, Milwaukee, Wis., a corporation of Delaware Application December 8, 1933, lSerial No. 'ZilLLiSZ 21 Claims.

This invention relates in general'to a. regulating system for parallel connected dynamo electric machines, and more particularly to such a. system in which it is desired to automatically maintain an equal or uniformly proportional division of load among the various machines irrespective of the number of machines connected in parallel. I An object of the invention is to provide a regulating system for a plurality of parallel connected generators or motors which will automatically maintain equal or uniformly proportional loads on a variable number of parallel connected generators or motors.

. Another object of the invention is to provide aregulating system for a plurality oi parallel connected dynamo electric machines each having interconnected load responsive windings associated therewith for controlling the excitation thereof and including switching means for deenergizing the windings associated with a ma.- 4 chine which has been disconnected from the remaining parallel connected machines so as to render the remaining load responsive windings effective to control the excitation oi the remaining machines to maintain equal or uniformly proportional loads thereon.

x Another object of this invention is to provide a regulating system for a plurality of generators which supplyenergy to a plurality o translating devices connected theretoy and which are connected in parallel by sectionalizing switches, the system including individual regulating means each having a plurality of interconnected load responsive windings and switches operated in response to the disconnecting movement of a sectionalizing switch to automatically deenergize the load responsive windings so as to automatically maintain equal or uniformly proportional load division on the remaining parallel connected generators.

A further object of the invention is to provide a regulating system having a plurality or" magnetlc devices each having a boosting winding and a plurality of bucking windings so interconnected as to denne a plurality of independent series parallel circuits, each circuit including one boosting winding associated with a magnetic device and a plurality of bucking windings severally associated with the other of said magnetic devices.

provide a. regulating system having a plurality oi magnetic devices each having a boosting winding and a plurality of bucking windings, each boosting winding having a plurality of diierent buck- ^A still further object .of the invention is toV ing windings connected in series with each other and across said boosting winding, and switches arranged to deenergize the windings of any one of the magnetic devices so that the total mmi'. of the bucking windings of each other device remains equal and opposite to the mmf. oi the remaining boosting windings respectively.

These and other objects and advantages are attained by this invention, various novel features of which will be apparent from the description and drawings herein, and will be more particularly pointed .out in the claims.

Various illustrative examples oi the application of this invention are shown in the accompanying drawings in which:

Fig. l is a schematic diagram of a regulating system embodying features o the present inven-a tion; Fig. 2 is a schematic diagram of a modified portion of the system of Fig. l;

Fig. 3 is a schematic diagram oi another form of regulating system embodying features of. the present invention; and

Fig. i is a schematic diagram oi another :form

of regulating system embodying features oi the present invention.

Referring now to Fig. i; and (i are positive and negative buses across which a translating device "l, here shown as an electric motor, is connected by means of switch 8. A plurality of dynamo electric machines A, B and C, here shown as direct current generators driven by prime movers (not shown), are connectable across buses 5 and E by means or' disconnecting switches do, lib and ic and overload circuit breakers da, 9h and 9c respectively. Machines A, B and are provided with separately excited eld windings lila, lb and ille respectively, and inter-pole windings ila, iii: and ilo respectively. These machines are also provided with windings i205, l2?) and iEc which are preferably compensating windings, however, they may also be series compound windings. The excitation oi the separately excited eld windings lila, mb and ic is controlled by eld rheostats Isa, 13b and i3c respectively which are selectively operated in one or another direction by means of reversible pilot motors Ma, Mb and idc respectively, noting that these field windings and pilot motors receive their energization from a control bus having conductors l5 and I6 which are preferably connected to a source oi.' power (not shown).

Each of the above described pilot ymotor actuated rheostats is controlled by means of a regulating device, here shown as of the solenoid relay type. These regulating devices have pilot motor lib the abovedescribed back contacts are with voltage responsive windings wa, iSb and I9c which are connected across the armature and series windings of machines A, B and C respec tively, noting that rheostats 2da, 20h and 26o are connected in series therewith. The regulating device associated with machine energized in accordance with the load on Inachines C and B respectively, and is also provided with a boosting winding 23a which is connected across interpole winding ila and winding I2@ through adjusting rheostat 38a. The regulating device associated with machine B is provided with bucking windings 2de and 2da which are energized in accordance with the load on machines C and A respectively, and is also provided with a boosting winding 25h which is connected across interpole winding lib and winding itilv through adjusting rheostat sib. The regulating device associated with machine C is provided with bucking windings 28h and 29a which are energized in accordance with the load on machines B and A respectively, and is also provided with a boosting winding alc'which is connected across interpole winding llc and winding i2c through adjusting rheostat 3lc. The regulating devices are provided with springs 32a, 32h and 32e respectively which serve to assist in balancing the magnetic pull on core members icl., lb and idc due to the potential winding thereon.

Overload circuit breaker 9a, as here shown, is provided with back contacts 33a and 36a. which are adapted to short circuit bucking windings Zic and 22h respectively. Circuit breaker 9b. as here shown, is vprovided with back contacts 35h and 36h which are adapted to short circuit bucking wind-A7 ings 24e and 26a respectively. Circuit breaker 9c,

as here shown, is provided with back contacts 37o and 38e which are adapted to short circuit bucking windings 28h and 29a respectively. Although mechanically connected to the respective circuit breakers, it is to be understood that these contacts may be operated by relays controlled by the respective circuit breakers as shown in Fig. 3.

When circuit breakers 9a, 9b and 9c are in their closed positions, the various bucking windings will not be short circuited, noting that bucking windings 35a: and 29a are connected in series with each other andacross boosting winding 23a. and that bucking windings 22h and 2th are connected in series with each other and across boosting winding 25h, and thatbucking windings 2l c and 2de are connected in series with each other and across boosting winding 27e. The hereinabove described bucking and boosting windings prefer ably have the saine number of turns and the same -resistance, however since certain of these windzfings may in practice be spaced further away from the solenoid cores than pthers, it is sometimesrdesirable to provide the bucking windings with auxiliary parallel connected resistors. Since the boosting windings 23a, 25h and 271e are connected across the interpole and compensating windings of the respective machines, they will each have a -denite mmf. when the currents owing through machines'A, B and C are equal, and since the buchng windings energized vin accordance with the load on the various machines are connected in series across ,various boosting windings. they -will each have a denite mmf. which, in the em- A is provided with bucking windings 2c and 22h which are bucking windings.

shown as Y bodiment shown, will be one-half of the mmf. of

the boosting windings. It is thus seen that with equal loads on each machine the total mmf. of the bucking windings of each regulating device will equal and oppose the mm1. of the boosting winding associated therewith, that is, the resultant mmf. of the bucking and boosting windy ings and each regulator will be zero when the loads on the respective machines are equal.

Although the invention has been shown as applied to a regulating system having three dynamo electric machines, it is to be understood that it may be extended toy a greater number of machines simply byconnecting the additional bucking windings of the additional machines in series with the other bucking windings. For example, in a. machine having n number of dynamo electric machines, each regulating device will have one voltage responsive winding, one boosting winding cumulativeiy related to the voltage coil and n-l winding carries r of the current in the boosting windings, it follows that for any number of machines the total mmf. of the bucking windings will equal and op- Inasmuch as each bucking pose the mmf. of the boosting winding associated therewith when the loads on the respective machines are equal. It is to be noted that the use of additional bucking windings will reduce the current in the` other bucking windings, however, since each regu-- lating device will then have additional bucking windings, the same essential relation of these i' windings will exist, namely that the total mmf. of the bucking and boosting windings of each regulating device should equal zero when the loads on the various machines are equal.

The operation of Fig. 1 is as follows: Assuming that switches 8, 8a, db, 8c and circuit breakers da, 9b and Scare all in their closed position and that generators A, Band C are delivering currents oi equal value to bus conductors 5 and G and that the voltage across bus conductors and 6 is normal, the magnetic core members iSd, ib and i 8c will remain in their neutral positions and pilot motors ida, ib and idc will remain idle. Ii, after increase or decrease oi the load on translating device l, the currents through the maaction will occur unless the increase or decrease of load was such as to cause an appreciable change in the voltage ofthe generators. If the above described change in load causes the voltage chines A, B and C remain equal, no regulating' on bus conductors 5 and 6 to drop, the magnetic pull on each core member la,v l8b and .itc will be decreased thereby permitting springs 32a @2b and 32e to move contact mechanisms ila? lib and Hc ;ir upper positions therebi/causing pilot motor vta, Mb and idc tomov rheostats? 03a, i135 and 93e in such a direction ,as to increase the excitation of windings ida, ib and ic respectively. Ii the voltage across'fbus conductors E and E rises, magnetic core members ita, i817 and idc will belcaused to move upwardly thereby,

causing pilot motors ida, Mib and idc to operate in such a direction as to decrease the excitation oi eld windings itia, ith and ille. It is thus seen thatV with equal loads on the various generators,

voltage coils ida, i912 and i90 are eective to. 'maintain constant voltage on bus conductors vt3 and d, noting that the magnitude of this Vvolt= is alsov provided with additionalcontacts 'lib and, dsc thel purpose of which will be described hereinafter.' Similarly the bucking andboosting windings of the regulators associated with m9,-,a 5 chine B- are deenergized by means -oi contacts 35h, 36bland 52h, noting that relay 43h which 'is 4controlled by front contact Mib-shown on over-- load circuit breaker 9b, is also provided with addi-- tional contacts'a and 50c for la purpose which will be described hereinafter. Similarly the buckingandl boosting-windings of the regulator associated with the machine C are deenergized' by contacts 37e, 38e and 53c of relay 43e, the energization of which is controlled by front contacts Mc on overload circuit breaker 9c and iront contacts it on sectionalizing switch titi, noting that relay 43e has additional contacts a and li'b for a purpose which will be described hereinafter.

The operation of Fig. 3 is as follows: Assumingpthat sectionalizing switches 3b and d@ are closedand that all of the generators and transV lating devices are connected in parallel across bus conductors 5 and o and that the loads on the respective generators are equal, the total mint.y of the bucking and boosting windings of each regulator will be zero and the armature voltage oi exciters dia, ilo and die will therefore also be zero.' Voltage windings 59a, lsb and itc are 3@ therefore ective to 'maintain constant voltage on bus conductors E and 6 in a 'manner sub= stantially the same as described inconnection with Fig. l.

Assuming that the load on the 'generators changes so that generator A is carrying more than its share o the load, then the mmf. of boosting' winding 23a will be greater than the total mmf. of the bucking windings 2l c and 22h thereby cause ing auxiliary'generator lia to produce a voltage cumulative with respect to normal voltage on e winding 99a thereby vincreasing the energlzation of winding 99a. 'Ihe increased magnetic pull on ,core member Iba operates switch mechanism ila and thus 'causes pilot motor ld to rotate rheostat isa; in such a direction as to decrease the excitation vof eld'wlnding ita. At the same time the mmf. of bucking windings 26a and 2te is decreased thereby causing auxiliary generators dit and ti ci to produce voltages which oppose thenormal-voltage impressed on'windings i972 and isc respectively, thereby decreasing the energization of windings isb and itc. The den creased pull on core members leb and idc causes contact mechanisms lib and vilc to energize pilot motors lib and idc in such a direction as to in= Y' crease the excitation of eld windings ich and' idc respectively. Similarly iil 'generator A is carrying less than its share of a'load, the regulator associated therewith will operate to increase the excitation thereof andthe regulators asso4 ciated with generators B and C will operate to decrease theexcltation of held windings ich and itc in a manner apparent from the above description. y

If a generator, such as A, is disconnected from circuit for any reason, as for instance, through action citan operator when the total load -is relatively light, actuation of the circuit'breaker @a to open position causes opening oi contacts fida, thus deenergizing relay lima Relay ia'inu moving toits lower position causes contacts 33a and' 34a to short' circuit bucking windingsjla and 22h and also deenergizes boostingwinding 23a and bucking windings 26a. and 29a.- by opening contact Ela. The opening of* contacts Wb.

and'- 69e at this time causes no control operations inasmuch as they are shunted by contacts 48h and :50c respectively.

Ii it is desired to energize translating device flic solely from generator A, sectionalizing switch it 5 may be opened thereby disconnecting generator A from the parallel connected generators B and C. The opening of sectionalizing switch 39 also opens contacts 46 (noting that contacts @da are closed at this time) thereby deenergizing relay lv 43a. The downward movement of relay dta deenergizes the bucking and boosting windings of the regulator associated with generator A in the manner described in the preceding paragraph.

If it is further desired to energize translating l device 'ic solely from generator C, sectionaiizing switch d@ may m opened. The opening oi sectionalizing switch d@ also opens contact d5 and thus deenergizes relay lec. Relay 33e upon moving downward short circuits bucking windings 20 2th and 29a by means of contacts die andrec and disconnects boosting winding 27o, noting that winding Ello is normally connected across inter= pole winding lle and compensating winding idc by means of contacts 53e and 50c. The regulator 25' associated with generator C will then function as a constant voltage regulator to supply translating device ic with a voltage which may be varied by means of rheostat 2de. If overload circuit Vbreaker 9c trips at a time when sectionalizing 30 switch d@ is closed and sectionalizing switch 3s is open, relay 33e will move downward and will deenergize boosting and bucking windings die, 2th and 2da in the manner above described. it is to be noted that under these conditions contacts dit and idbwill both be open thus disconnecting boosting winding 2th and thus permitting the regulating ,device associated with generator B to act as a constant voltage regulator controllable by rheostat 2do. Although the overload circuit 40 breakers and sectionalizing switches may be opened or closed in a great number of dierent ways or combinations, the main results accounpllshed by the operation of these switches have been described and it will be apparent from in- 45 spection of the drawings that proper regulating action will be obtained no-matter what the operating i positions oi the' various sectionalizing switches and circuit breakers may be.

It will be apparent that instead of having the aumliary generators `dla, sib, die oi Fig. 3 in series with the voltage windings isa, isb, isc, respectively, the latter windings may be supplied wholly from the terminals of the respective gen-= erators, with each of the auxiliary generators supplying energy to an auxiliary winding provided on the core ida, lsb, itc oi' its respective regulator and producing through such windings cumulativeor dierential energizing eiects on such cores as may be required to produce the 6o desired balanced regulation of the main generators. v

Figa shows a regulatingsystem in which the generators A, B and C are connectable in parallel by means of overload circuit breakers to, sb and 6 5 sc.- Auxiliary generators 56a, 5th and 5to areF preferably driven by generators A, B and C, a1- though they may be driven by separate prima movers. If there are n number of exciters, each exciter will have one main held winding, herein Z indicated as being separately excited from the armature of the. main generator A, and preien1 ably with a suitable regulating rheostat included in the circuit oi such .eld winding, and one load responsive boosting winding and n-l load responsive bucking windings. For example, exciter 456a has a magnetic pole member 51a on which are wound voltage responsive winding l9a, boosting winding 23a and bucking windings 2Ic and 22h. It is to be noted that the iield windings of the various exciters in Fig. 4 are connected inthe same manner as describedl inV connection with Fig. 1, however, it is to be understood that they may also be connected as shown in Fig. 2. During normal conditions, each exciter will generate a voltage due solely 'to its voltage responsive winding inasmuch I as bucking windings thereon normally cancel'the mmf. of the boosting winding thereon. It vwill thus be apparent from the above description in connection with.

Figs. 1 and 3 that any unbalance of current among the various generators will cause the exciters to raise or lower their voltage and thereby maintain the loads on the various generators equal. It will also be apparent from the above description that the disconnection of any one or more of said generators upon overload will deenergize the corresponding bucking windings so that the remaining parallel connected generators will beautomatically rendered eiective to regulate in the manner that will be-apparent from the above description. Infsome instances, it may be desirable to omit exciters 56a, 56h and 56e and to connect the various voltage responsive windings, boosting windings and bucking windings so as to energize the iield poles of the main generators A, B and C directly. For example, winding Illa of generator A may be substituted by windings of the relative proportions of and connected in circuit similar to Isa, Zic, 22h and 23a.

It will be apparent that where the machines A, B, C arenot of the same normal rating, the several boosting and bucking windings acting on the extended cores oi the regulators are suitably dimensioned to provide the ampere turns required for producing the desired regulating eiects on any' departure from the desiredproportional distribution of load on the several machines; and where reference is made herein to equalizing the load division or the maintenance of equal load division on the several machines, it is contemplated that such expressions apply as well to the maintenance oi uniformly proportional loads on the several machines, where the loads on the several machines are desired to be maintained at unequal values. Y

Although the above4l described embodiments have been shown as being direct current generators, it is to be understood thatthe invention is also applicable to the control of direct current motors, through regulation of the iields of the motors, or generators supplying such motors, where it is desired to maintain constant relative load on such motors. And the invention is also applicable to the control of a plurality of alternating current generators supplying a common load for balancing the wattless component of load between the several generators where it is desired to maintain constant bus voltage, in which-caseV ent invention have been illustrated and described,

it will be apparent from the following description that various changes and modifications .may be made therein without departing from the spirit of the invention or from the scope of the ap-L pended claims.

It is claimed and desired to secure by Letters Patent:

1.1In combination, more than two dynamoelectric machines each having a ileld winding, switching means selectively operable to connect two or more of said machines in parallel, means for individually varying the excitation of said field windings respectively, and means for automatically controlling each of said excitation varying means respectively so as to secure a substantially constant proportional distribution of the loads on the machines connected in parallel, each of said controlling means comprising a winding energized in accordance with the load on the machine associated therewith and other windings each energized in accordance with the load on one of a plurality of said other parallel connected machines, said other windings normally neutralizing said rst mentioned load energized winding.

2. In combination, more than two dynamoelectric machines each having a i'leld winding, switching means for selectively connecting two or more of said machines in parallel, means for varying the excitation of each of said field windings, means for automatically controlling each of said excitation varying means individually so as to secure a substantially constant proportional distribution of the loads on the machines connected in parallel, each of said controlling means comprising a boosting winding energized in accordance with the load on the machine associated therewith, and each further comprising additional energizing means energized in dependence upon the load on each of the other parallel connected machines, and aurdliary switches operable to rendersaid additional energizing means indeenergized in accordance with the load on the machine associated with said controlling means respectively and comprising a plurality of bucking windings energized in accordance with the load on each of the other ofsaid machines respectively, and means actuated upon disconnecting movement of one of said switching means to deenergize the windings of the-controlling means associated with the disconnected machine.

4. In combination, more than two dynamoelectric machines each having a ileld winding, switching means for connecting said machines in parallel, a plurality of devices arranged to individually vary the excitation of said field windings respectively, a pluralityv of electromagnetic devices arranged to control said excitation varying devices respectively to maintain a substantially constant proportional distribution of loads on said machines, said electromagnetic devices each comprising a boosting winding connected for the machines connected in parallel. each of said Y controlling means comprising a boosting winding 6 i aossnsa energization in accordance with the load on the machine associated with the respective electromagnetic device, and each comprising a plurality of bucking windings each connected for energi- I zation in accordance with the load on the individual ones of the other oi said parallelconnected machines respectively, said bucking and boosting windings being so proportioned that their combined magnetic effect on each of said chines respectively, atleast one sectionalizing switch arranged to selectively connect two or 25 nidi-e of said machines in parallel, a plurality oi' devices arranged to individually vary the excitation of said eld windings respectively, a plurality of electromagnetic devices arranged to control said excitation varying devices respectively so as to'maintain a predetermined'division be- 'tween the loads on said machines. said electromagnetic devices each comprising a winding energized in accordance with the load on the machine controlled thereby and comprisingl a 35' pluralityof differential windings energized in Y accordance with the load` on the other, parallel connected machines, and switching means operable in response to the opening of one of said sectionalizing switches for deenergizing certain of 40 said differential windings.

6. In a regulating system for a plurality of parallel conected dynamo-electric machines, the

combination oi' a plurality of excitation regulating devices each having a winding energized in 45 accordance with the load on one of said machines and each having a plurality of windings energized in accordance with the load on the other of said parallel connected machines respectively, the

windings of the respective regulating devices Aiii) which are energized in accordance withthe load on the same machine being connected in sexiesparallel, and switching means for selectively deenergizing certain oi.' said windings.

'1. In a regulating system for' more than two 55 parallel connected dynamo-electric machines, the

combination oi a plurality of devices for regulating the excitation of said machines, each of said regulating devices having a boosting winding arranged to be energized in accordance with the 80 load on the machine associated with the respective device and each of said regulating devices having a plurality of bucking windings arranged 'to be energized in accordance with the-load on each of the other of said machines respectively,

and switch means selectively operable to deenergize the windings of one or more of said regulating devices,`the windings of each of said devices being so connectedand proportioned that the total mmf. oi the energized bucking windings there- 70 of normally equals and opposes the mmf. of. the

energized boosting winding thereof, Y

8. In combination, a plurality of magnetic devices each having a boosting winding and a plurality oi' bucking windings, means defining a plu- 75 rality of circuits each'including one of said boosting windings and aplurality of said bucking windings connected in series with each other and across said one of said boosting windings, each winding included in each circuit being associated with a diierent one of said magnetic devices. and 6 means for selectively rendering ineiIective the bucking and boosting windings of any of the said magnetic devices without aiiecting the desired operation of the remaining one or ones of said magnetic devices. l0

9. In combination, a plurality of magnetic de vices each having a boosting winding and a plurality oi bucking windings, and means deiining a plurality of circuits each including one of said boosting windings and a plurality of said bucking windings connected in series with each other and across said one of said boosting windings, each winding included in each circuit being associated with a dierent one of said magnetic devices, and each o said boosting and bucking windings having substantially the same number of turns.

l0. In combination, a plurality of magnetic devicesl each having a boosting winding anda plurality of bucking windings, means dening a plurality of circuits each including one of said boosting windings and a plurality of said bucking windings connected in series with each other and across said one of said boosting windings, each winding included in each circuit being associated with a diierent one of said magnetic devices, and p a plurality of switches selectively operable to'V short-circuit the bucking windings associated with said magnetic devices respectively.

`il. lIn combination, n number of magnetic devices, n being greater than two, each having one boosting winding and n minus one bucking windings arranged to excite said magnetic devices, means defining n circuits for energizing all of said windings, each circuit including n minus one 40 l bucking windings connected in series with each* other and across one of said boosting windings, each winding included in each of said circuits being associated with a diierent one of said magnetic devices, and means for selectively rendering ineiective the bucking and boosting windings of any of the said magnetic devices without affecting the desired operation of the remaining'one or ones of said magnetic devices.

12. In combination, n number of magnetic devices, n being greater than two, each having one boosting winding and n minus one bucking windings arranged to excite said magnetic devices. means defining n circuits for energizing all of said windings, each circuit including n minus one bucking windings connected in series with eachl other and across one of said boosting windings, each winding included in each of said circuits being associated with a diierent one of said magnetic devices, said windings being so -proportioned that with equal voltages applied to each of said circuits the total mmf. of the bucking windingsassociated with each oi' said magnetic' devices equals and opposes the mmf. of the boosting winding associated with each of said magnetic devicesrespectively, and switch means for selectively deenergizing the windings associated with any one .of said magnetic devices so as to maintainequalgand opposing mmfs. in the remaining energized windings. Y

13. In aregulating system, the combination of n number, greater than two, of dynamo-electric machines connected in paralleL'means for exciting each of said machines so as to maintain o. substantially constant proportional distribution -l =of the loads thereon comprising a-xvoltage responsive excitation winding for each machine and n diierentially related load responsive excitation windings for each machine, said excitflng means comprising means for connecting said windings energized in accordance with the loadsv on the other parallel connected machines respectively, said load responsive windings being so proportioned that the total mmf. ofthe load responsive windings'. associated with each machine normally equals zero, and means operable to selectively deenergize all of the load responsive windings of any of said machines while insuring that the mmf. of the load responsive windings associated with each of the other parallel connected machines normally remains equal to zero.

14. In a load equalizing system, the combination of n number, greater than two, of generators, a translating device for each of said generators, means for selectively connecting said translating devices across said generators respec- 1 tively, means selectively operable to connect two or more of said generators in parallel, each of said generators having excitation controlling means comprising a winding energized in accordance with the voltage of said generator, and

each having a winding energized in accordanceA with the load on said generator, and each having n minus one windings energized in accordance with the load on the other of said generators, said load energized windings being so proportioned and interconnected that their mmf.s

with respect to each generator exert a correcy tive eilect thereon on departure from normal division of load on said generators to`cause 4said generators to return toward said normal Aload division, and means operable in response to disconnection of one of said generators from said parallel connection for insuring that the excitation controlling means of the remaining one or more generators in parallel Vconnected service function to maintain the desired voltage and load iconditions on said generator or generators.

15. In a load equalizing system, the combination of n number of generators, a translating device for each of said generators, means for selectively connecting said translating devices across said generators respectively, sectionalizing switches selectively operable to connect two or more of said generators in parallel, each of said generators having exciting means comprising a winding energized in accordance with the voltage of said generator, and .each having a winding energized in Vaccordance with the load on said generator, and each having n minus one windings energized in vaccordance with the load on the other of said generators, said load energized windings being so proportioned and interconnected that their mmffs with respect to each f generator are normally zero, and switching'means loads on the machines connected in parallel, each of said controlling means comprising a .winding energized in accordance with the load aon the machine associated therewith and a plurality oi other windings each energized in accordance with the load on one of said other parallel connected machines.

17. In combination, more than twoA dynamaelectric machines each having a eld. winding, switching means selectively operable -to connect -two or more of said machines in parallel', means for individually varying the excitation of `said eld windings respectively, and means for automatically controlling each of said excitation varying means respectively so as to secure a predetermined desired propoftional distribution oi the l loads on the machines connected in parallel, each of said controlling-means comprising a winding energized in accordance with a characteristic of the load on the machine associated therewith and a plurality -of other windings each, energized in accordance with a characteristic of the load on one of said other parallel connected machines..

and means operatively dependent on the connec-` tion in or disconnection from parallel relation of any of said machines for rendering effective or ineffective, respectively, the desired controlling action of the controlling means associated with said latter machine.

. 18. In combination, more than two dynamoelectric machines each having a field winding, switching means selectively operable to connect two or more of said machines in parallel, means for individually varying the excitation ot said eld windings respectively, and means for automatically controlling each oi said excitation varying means respectively so as to secure a predetermined desired proportional distribution oi the loads on the machines connected in parallel, each of said controlling means comprising a winding energized in accordance with an electrical characteristic of the load on the machine associated therewith and a plurality of other windings each energized in accordance with an electrical characteristic of the load on. one of said other parallel connectedmachines, and means operatively dependent on the connection in or disconnection from parallel relation of any Vof said machines for rendering effective or ineffective, respectively, the desired controlling action of the controlling means associated with said latter machine and without affecting the desired controlling action of the controlling means of said other machines.

19. In combination, more than two dynamoelectric machinesV each having a field winding, switching means selectively connecting two or more of said machines in parallel, means for regulating the excitation effects of each of said ileld windings to maintain desired voltage regulation of Vthe particular machines when voperating alone, and means for automatically controlling the excitation-"regulating neans of each of said machines individually so as to maintain a substantially constant Vproportional distribution o! the loads on the machines connected in parallel,

. `each of said (controlling means comprising a windcontrolling means is associated, and a plurality dof bucking windings each energized in accordance with the load on another of several other parallel connected machines, said first windingsand said bucking windings of the several controlling means being so relatively proportioned and connected that the resultant magnetic eect exerts a minimum correcting eiect on said excitation regulating means when the loads on said parallel connecting machines are distributed in the desired proportion.

20. In combination, more than two dynamoB electric machines, means selectively operable to connect two or more of said machines in parallel, each of said machines having excitation controlling means comprising an exciter for a eld winding of said machine, said exciter having a sectional field winding including a portion whose energization is dependent upon the load on said machine and a portion whose energization is dependent upon the load on the other machine or machines connected in parallel with said first machine, said portions of said latter eld winding being so proportioned and connected with respect to the severalmachines as to exert a correcting eiect thereon on departure from normal division of load on said machines to cause said machines to return toward said normal load division, and

spaanse means operable in response to the disconnection of one of said machines from said parallel connection for insuring that the excitation controlling means o! the remaining one or more generators in parallel connected service function to maintain the desired voltage and load conditions on said generator or generators.

2l. In combination, more than two generators, means selectively operable to connect two or more of said generatorsin parallel, each of said generators having means for controlling the excitation thereof to insure desired voltage regulation of the generator when operating alone and also when operating in'parallel with one or more of 'said 'other generators and to insure a predetermined division of load on the several generators when operating in parallel, said excitation controlling means comprising anyauxiliary generator having a sectional iield winding including a portion whose energization is dependent upon a lcharacteristic of the load on said generator and a 'portion whose energization is dependent upon a characteristic of the load on the other generator or generators connected in parallel with said first generator, the portions of said latter Winding being so proportioned and connected with respect to the several generators as to exert minimum corrective eect under conditions of desired division of load on said generator.

- PAUL M. STIVENDER. 

